async_iterable not supported by ReSpec

[danielpeintner]

Description of problem

The new way of using async iterable is to use async_iterable
see whatwg/webidl#1504

Anyhow, using the new syntax shows problems with ReSpec

URL to affected spec or repo:

https://w3c.github.io/wot-scripting-api/#respec-offender-no-matching-definition-found

What happened (e.g., it crashed)?:

Error showing

Expected behavior (e.g., it shouldn't crash):

No error/warning

@saschanaz
see w3c/wot-scripting-api#579

[marcoscaceres]

Was implemented as part of w3c/webidl2.js#819 ... so we need to just update the WebIDL parser.

[marcoscaceres]

Ah, it's actually WebIDL's spec's "fault" 🤭
whatwg/webidl#1540

[sidvishnoi]

Fixed by whatwg/webidl#1541.